1. Field of the Invention
This invention relates to the field of protecting perishable products, in particular agriculture products, for market, and more specifically to a method and apparatus for surrounding agricultural products with a controlled atmosphere.
2. Description of the Prior Art
It is known that the ripening of agricultural products such as strawberries and tomatoes are affected by the atmosphere surrounding the product. It is, of course, desirable to control the ripening of fruits so that they can be delivered to the consumer in a ripe, but not spoiled condition.
Devices are known for storing fruits in a protective atmosphere or for providing a protective atmosphere with trucks and box cars. These devices utilize a purge technique, to replace the air atmosphere within the container with the desired atmosphere. The desired atmosphere flows into the container and the displaced atmosphere is vented out of the container. Thus, there is a continuous mixing and dilution of the atmosphere within the container, until the original air is almost totally expelled.
Because of the mixing of the atmosphere, this known method is costly, is inefficient, is wasteful of the purging gas, and requires a long time to expel the original atmosphere. The time is further increased if the product is packaged in a stack of individual boxes resulting in a labyrinth for the gases to follow. Additionally, differences in temperature of the gas within the container can result in stratification, and can further delay complete protection of the product. Stratification is always a problem when purging, in that the purge gas can pass by the surfaces of the product due to the prior atmosphere forming, with the purge gas, a stratified layer in the container. Higher pressures of purge gas will aid in reducing such stratification, but, especially deep inside a pallet of product containers, the lower velocity of the purge gas is ineffective to eliminate stratification altogether.
It is the gases that are adjacent the surface of the fruit which affect the ripening of the fruit. Some of these gases are held in contact with the fruit by adsorption and absorption of the gas on the fruit's surface. A simple purging of the atmosphere does not repidly remove these localized gases. Thus, the fruit may continue to ripen, because these adhering gases are not adequately removed by the prior art purge technique.